One of several approaches to the treatment of cancer is the promotion of differentiation of malignant cells into histologically and clinically benign lesions. Malignant cells in human acute and chronic lymphocytic leukemias and lymphomas of B cell origin most frequently exhibit an arrest of maturation as shown, when studied by immunofluorescene, by the presence of monoclonal surface-associated immunoglobulin, without secretory-intracytoplasmic immunoglobulin, and without the corresponding serum monoclonal immunoglobulin. This study will concentrate on in vitro stimulation of maturation of cells from patients with lymphoid malignancy of B cell origin by exogenous cyclic AMP and cyclic GMP, by substances and drugs which elevate endogenous cyclic nucleotides, and by pokeweed mitogen. The role of Ca ions in the process of maturation of malignant and non-malignant B lymphocytes will be studied by using ionophores. Malignant human lymphoid cells and cryostat sections of solid tissues will be studied for B-, T-, and M- (monocytic) cell receptors. Pulse and prolonged exposure to substances triggering maturation will be done in vitro. Quantitation of cells bearing surface-associated (receptor) immunoglobulins and of cells containing intracytoplasmic (secretory) immunoglobulins will be done by immunofluorescence. Secreted immunoglobulins in tissue culture will be measured by radioserological assay. Normal lymphocytes from volunteer donors and established cell lines of B- and non-B-origin will serve as a control.